Electric lamps of the vibrating filament type having a conductive coating

ABSTRACT

An incandescent lamp having a movable filament therein which is caused to oscillate in response to the field from a magnet in which at least a portion of the surface of the lamp envelope is coated with an electrically conductive material.

United States Patent 1191 Thouret et a1,

[ June 4, 1974 1 ELECTRIC LAMPS OF THE VIBRATING FILAMENT TYPE HAVING ACONDUCTIVE COATING [75] Inventors: Wolfgang E. Thouret, Verona, N.J.;

Rudolph Kaufman, Bronxville,

[73] Assignee: Duro-Test Corporation, North Bergen, NJ.

22 Filed: Sept. 5, 1972 121 App]. No.2 286,551

52] us. c1 313/313, 313/160, 313/291,

581 Field of Search 315/267; 313/313, 110,

[56 1 References Cited UNlTED STATES PATENTS 2,079,085 5/1937 Richter etall 313/313 X 2,419,177 4/1947 Steadman 313/110 X 2,456,474 12/1948Wainwright 313/313 X 2,654,042 9/1953 Clarke et 211. 313/291 X 2,714,6838/1955 Jenkins 313/291 X 3,200,280 8/1965 Thau et a1 313/110 3,355,61711/1967 Schwartz et a1. 313/313 X 3,549,946 12/1970 Kyp 315/267 PrimaryExaminer-Alfred L. Brody Attorney, Agent, or FirmDarby & Darby v 71ABSTRACT An incandescent lamp having a movable filament therein which iscaused'to oscillate in response to the field from a magnet in which atleast a portion of the surface of the lamp envelope is coated with anelectrically conductive material.

7 Claims, 5 Drawing Figures ELECTRIC LAMPS OF THE VIBRATING v FILAMENTTYPE HAVING A CONDUCTIVE COATING Decorative incandescent lamps withvibrating filaments that simulate the flickering movements of a candleflame are commercially available. Lamps of this type have a filament ofa relatively thin and flexible material which is formed in a loop of adesired shape. A permanent magnet is mounted either inside the glasslamp bulb or on the outside of the bulb with its magnetic field orientedto react with alternating current flowing through the filament to causethe lamp filament to vibrate. Thealternating current applied to thefilament is also of a magnitude to make the filament incandesce so thatthe impression of a flickering live flame is created for the purposes ofesthetic appeal. A lamp of this. general type is disclosed in US. Pat.No. 3,237,053 and French patent 368,913.

Some lamps of the foregoing type, out of-a batch which are made by thesame manufacturing techniques,

An additional object is to provide an electric incandescent lamp with avibrating filament having a conwhich:

become inoperative, that is, cease vibration, or begin to vibrate onlyslowly or intermittently after a relatively short period of time ofoperation. One reason for this, among others, is that the glass bulbaccumulates an electric chargeon its surface. This charge in turncreates a relatively strong electric field between the inner wall of thelamp bulb and the filament. The electric field produced by thestatic'charge electrically attracts the filament, which is relativelythin and flexible. In some cases, the attraction is strong enough sothat the filament will be moved completely over to the wall of the bulbwhere it will be held. This, of course, renders the bulb inoperative forits intended purpose of producing a vibrating filament.

The static charge is held by the bulb for a long period of time, due tothe excellent insulating properties of the glass. in some cases, it ispossible to discharge the builtup static charge merely bytouching thelamp bulb. However, in other cases, this simple expedient will not work.When the thin filament is attracted against the bulb wall by theelectric charge. it is often permanently damaged thcrcbyrenderin g thelamp useless even if the static charge could later be dissipated.

The present invention relates to lamps of the vibrating filament typeand more particularly to an arrangement for preventing the buildup of astatic electric charge on the glass lamp bulb. In accordance with theinvention, a coating of a light-transmitting electrically conductivematerial is deposited on the inside, the outside, or both walls of thebulb. The conductive coating, which is returned to an electric neutralpoint, acts to dissipate the electric charge which would be built up onthe lamp bulb. The coating may also be of a suitable type, forexample ofa desired color, so as to produce a novel decorative effect. Thus, thecoating performs the dual function both of reducing the buildup of thestatic electric charge and also of serving as a decorative coating. Thelatter is particularly esthetically pleasing when used in combinationwith thevibrating incandescent lamp filament.

It is therefore an object of the present invention to provide a novelincandescent lamp of the type having a vibrating incandescent filamentwith a coating of conductive material on one of'the walls of the bulb toreduce the static electric charge buildup.

FIG. 1 is an elevational view, partially broken away, of a lamp made inaccordance with the invention;

FIG. 2 is an elevational view similar to FIG. 1 the turn with respectthereto;

FIG.- 3 is a view similar to that of FIG. 2 of another embodiment of theinvention;

FIG. 4 is a cross-section of a fragment of the lamp bulb wall of FIG. 3;and

FIG. 5 is an elevational view similar to FIG. 1 showing anotherembodiment of the lamp.

Referring to FIGS. 1 and 2, the lamp of the subject invention includesthe usual glass bulb 12 having a threaded base 13 which forms oneelectrical contact 14 for connection to an alternating current supply(not shown) and a second contact 15 at its bottom. This is aconventional lamp construction. lt shall be understood that otherconventional base constructions, for example a bayonet base, also can beutilized.

A filament 18 having the shape of a loop extends upwardly from a glassstem 20 mounted within the lamp bulb. The filamentis mounted at its ends18a and 18b to a pair of lead wires 21a and 21b which'pass through stem20 and are respectively connected to the contacts 14 and 15 of base 13.The connection between the ends of the filament and the lead wires canbe made by any suitable arrangement, for example, by the use of asuitable electrically conductive cement. The filament 18 is preferablymade of carbon and is relatively thin and flexible so that it canvibrate in a desired pattern. The filament itself is shaped as desired.

A pin 22 is mounted in the stem 20. The pin is not electricallyconnected to any other part of the lamp. It has a loop 23 at its upperend to hold a permanent magnet 25. The permanent magnet, which can be ofmetal, ceramic, or any other suitable material, is shown illustrativelyas being of elongated bar shape. It should be understood that anysuitable shape can be utilized. Also, it should be understood that thepermanent magnet can be located on the outer wall of the bulb.

The permanent magnet is oriented with respect to the filament 18 so thatits magnetic field reacts with the alternating current applied to thefilament to cause the filament to vibrate, pivoting about the connectingpoints to the lead wires, in accordance with the classical physicalreaction of electromagnetic theory wherein a magnetic field reactingwith electric current will produce motion. Sincealternating current isused, the motion generally will be in opposite directions on each sideof the plane of the filament when it is at rest.

It has been found that for some reason the motion of the filament 18will eventually cause a static electric charge to build up on the wallof bulb 12. The theoretical reason for the charge build up is notentirely known erably, or weakens the vibrational amplitude. In somecases the filament is permanently damaged when it engages the bulb walland will stop vibrating entirely or break and thereby render the lamptotally inoperative.

In accordance with the invention, the foregoing disadvantages areovercome by coating at least one of the wall of the bulb with a thin,light transparent electrically conductive coating. It is preferred thatthe coating be at least on the inner bulb wall. This is shown in FIG. 2wherein the coating 30 fully coats the inner wall of the bulb. It alsoextends over at least a portion of the stem to make contact with one ofthe leads 21a or 21!). This connects the coating to the neutralelectrical points of the alternating current power supply on alternatehalf cycles of the applied voltage to discharge any static electriccharge which is built up on the bulb wall. lnstead of using the coatingmaterial to connect the coating to one of the lead wires, a conductivewire or strip can be utilized.

The conductive coating can be of any suitable material which has thenecessary electrically conductive properties. For example, it cancomprise a metal such as aluminum, silver, gold, copper, tin, etc. Itcan also comprise another electrically conductive compound, for example,tin oxide. Some semi-conductive compounds, for example galliumphosphide, gallium arsenide, indium arsenide, mercury selenide, also canbe used. This will provide a slower rate of leak-off of the charge. Thecoating and its thickness are selected so that the bulb will still havesubstantial lighttransmission quantities for the light given off by thefilament. This can be accomplished by depositing on the bulb wall byevaporation or cathode-sputtering under vacuum, or any other suitablemethod, the desired thickness layer of the coating material being used.Such coatings can be made very thin, as small as about ten angstroms.

While the coating layer will absorb some of the light emitted from theincandescent filament 18, this absorption can be kept relatively low byusing a very thin layer of the conductive material. Even when theoptical absorption of the coating layer or layers is adjusted to lessthan 10 percent of the incident visible light, the electricalconductivity can be entirely sufficient for the purpose of thisinvention to prevent the accumulation of an electrical charge on theglass bulb wall. It should be understood that the coating material 30can be selected for a particular esthetic effect, for example, by coloror by the pattern of deposition.

H08. 3 and 4 show another embodiment of the invention. Here a coatinglayer 30 is deposited on the inner bulb wall and a layer 32 on the outerbulb wall. As before, the coatings are of any suitable electricallyconductive material. The inner layer 30 is again electrically connectedto one of the lead wires 210 or 21b, whichever is the one electricallyconnected to the threaded portion 14 of base 13. The outer layer 32 alsohas a lower portion 33 which extends to make electrical contact with thethreaded portion of the base 13. Since both the inner and outer coatings30 and 32 are connected to the same electrical point there is nopotential gradient between the two coatings and a charge cannot be builtup. ln some cases it might not be necessary to make the extendingportion 33 since the threaded part of the socket into which the lamp isscrewed would normally make contact with the lower end of the bulb.

In some applications, for decorative lamps with vibrating filaments, acertain amount of light adsorption through an electrically conductivelayer on the glass bulb is desirable. If the coating is properlyselected, the light absorption or partial absorption and partialreflection of the light from the filament on the opposite bulb walls canproduce interesting and pleasing decorative optical effects. Further, ifthe electrically conducting layer is made extremelythin, it can producemulti-color effects through optical interference, thus creating theappearance of an irridescent coating on the lamp bulb. In some cases,the desired decorative effects can be obtained without electricallyconnecting the outer coating 32 to the source of alternating currentvoltage. It has been found that the inner coating provides the mostsignificant effect with respect to the prevention of chargeaccumulation.

The accumulation of electrical charges can in many cases also beeffectively prevented by coating the bulb only partially. As shown inFIG. 5, only the lower half of the bulb inner wall surface, from thebulb neck to the semi-spherical bowl of the bulb, has a coating 30athereon. ln general, the coating does not have to cover the entire bulbsurface, either inside or outside.

Other suitable patterns, or configurations, for the coating also can beused. For example, a wire mesh" or other suitable configuration whichprovides an electrically closed surface can be utilized on all or aportion of the one or both of the bulb walls. This provides aninteresting decorative effect as well as seeming to prevent chargeaccumulation.

What is claimed is:

1. In an incandescent lamp the combination comprising, a bulb oftransparent vitreous material, an incandescent filament located withinsaid bulb, means for electrically connecting said filament to a sourceof alternating current, a permanent magnet located with respect tosaid'filament to interact with the current flowing therethrough toproduce vibration of the filament and to cause it to travel through asubstantial portion of the internal area of the bulb and adjacent theinner wall of the bulb, an electrically conductive coating of materialwhich is at least partially light transmissive on at least one of thewalls of said bulb, and means for electrically connecting said coatingto a point of potential with respect to said current source to leak awaya static electric charge from'the bulb.

2. A lamp as in claim 1 wherein said electrically conductive coating islocated on the inner wall of the bulb.

3. A lamp as in claim 1 wherein said electrically conductive coating islocated on the outer wall of said bulb.

6. A lamp as in claim 1 wherein said electrically conductive coating isarrayed in a predetermined pattern.

7. A lamp as in claim 1 wherein said electrically conductive coating isof metal.

2. A lamp as in claim 1 wherein said electrically conductive coating islocated on the inner wall of the bulb.
 3. A lamp as in claim 1 whereinsaid electrically conductive coating is located on the outer wall ofsaid bulb.
 4. A lamp as in claim 1 wherein the electrically conductivecoating is located on both the inner and the outer walls of the bulb. 5.A lamp as in claim 1 wherein the electrically conductive coating coversonly a portion of the surface of the bulb wall.
 6. A lamp as in claim 1wherein said electrically conductive coating is arrayed in apredetermined pattern.
 7. A lamp as in claim 1 wherein said electricallyconductive coating is of metal.